Posted on March 3, 2020 10:08 pm
 |  Asked by Igor Abakumov
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I am trying to calculate required bandwidth for some streams, and compare it to the output of “show interface eth 1-48 count rates” command. To make the comparison correctly i need to know whether Arista counts the layer 1 overhead (ethernet preamble + header + frame checksum + interframe gap) and layer 2 (IP header) in its count rates.

I have not found anything related in documentation for EOS.

Please point me to the part where this part (count rates with/without overhead) is described, or tell me where can i get such information.

Thanks in advance.

Posted by Alexander Bespalov
Answered on March 4, 2020 11:22 am

Hello Igor,

Which platform you are asking about?




Posted by John Gill
Answered on March 13, 2020 5:34 am

The rate shown show interface is the ethernet frame size including CRC but minus framing overhead.
We include the framing overhead in the percentage calculation next to this rate.

from show interfaces:
5 seconds input rate 951 Mbps (1.0% with framing overhead), 294305 packets/sec

or from show interfaces counters rate:
Port Name Intvl In Mbps % In Kpps Out Mbps % Out Kpps
Et60/1 0:05 949.7 1.0% 294 0.0 0.0% 0

The framing overhead consists of 20 bytes per packet:
12 bytes - interframe gap
7 bytes - preamble
1 byte - start of frame delimiter

John Gill

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